SME 20/2 Tonearm Ground Wire: Where in the table should be connected?

Much appreciated !

@vusi_khumalo 

Do u have and explanation on why not 'engaging the shielding' improves sound?

While I don’t care to discuss in absolute terms for fear of being attacked, unshielded signal leads can often provide a larger playback image that seems more open. Such results are worthless if RF or other noise creeps in - easily remedied when the shields are attached to ground.

Should I further break the join between these 2 ground wires from the L & R RCAs?

I see no benefit from disabling or attempting an asymmetrical shielding scheme.

Hi @boothroyd 

Above you wrote:
The second ground spade in the phono cable loom is simply to engage the shielding - it’s the two wires exiting the RCA rears joined together. I typically prefer this connection left hanging (not attached) unless noise is evident.
As I have the same equipment, I have just disconnected "the two wires exiting the RCA rears joined together" from the Phonostage grounding port and I think there is a slight improvement in sound.
I have 2 questions if you don't mind sharing:
Do u have and explanation on why not 'engaging the shielding' improves sound?
Should I further break the join between these 2 ground wires from the L & R RCAs?
Thanks
Vusi

As @lewm meant to say,  If it aint broke don't fix it. If you have already connected the tonearm's ground wire, the one at the RCA end then you are done. Connecting the other one may well form a ground loop. The extra wire was meant to ground the turntable and it sounds by your description that it is already grounded. Just wrap the wire up and tie it to the others with a tie wrap. It won't be the last loose wire in your life. 

First of all, if you have no hum or  noise problem, you may as well do nothing. The only value of grounding is to reduce or eliminate such problems. Second, ground is ground (like every other sweeping generalization, there are exceptions), so all ground wires can be theoretically connected to the same grounding point, in this case the ground lug on your preamplifier. Ideally, they are all at zero voltage. That’s really all you have to know about those ground wires. Others gave you a lot of good detail information specific to SME. 

As I recall . . .

The single ground wire (spade) in the phono cable loom is the main ground which connects to the phono preamp.

The second ground spade in the phono cable loom is simply to engage the shielding - it’s the two wires exiting the RCA rears joined together. I typically prefer this connection left hanging (not attached) unless noise is evident.

On a different ground point, many later V2 Motor Controller Units had an additional ground wire terminated with a ring terminal - meant to go to the ground post directly on the motor.

Great phono system! 🎶

Which version of the power supply do you have? V1 is a rectangular box with a rotary dial, V2 has a beveled part with push buttons.

I have V2, and there is no grounding wire from the power supply to the table. There is a grounding wire from the junction box (where the power supply is plugged in, and where the motor is plugged in) to a gold plated grounding post the underside of the top plate of the table. There’s another gold plated grounding post attached to the AC motor, but without anything attached to it. This is how the table was configured when I bought it new.

How to upload photos into a post:

https://forum.audiogon.com/discussions/how-to-upload-photos-in-a-post

You can upload pictures in your virtual system!

Dear @yogiboy, @pcosta ​​​​@dogberry,

Thanks so much for your replies with suggestions, instructions and attachments. They are much appreciated. Please before to continue, I would like to share that I purchased the 20/2 with its IV VI in pristine condition, with its original boxes, documentation, manuals, tools, etc. etc. Regardless of all of that, I'm still don't know how to connect the ground's wires; but the good news is: I don't have any hums. Additional: For this basement application, I don't have a dedicated phono preamp; instead I'm using the one from the MA12000 (I don't know if its good or bad; I don't have nothing handy to compare). 

Back to the ground's connection:

1. The SME 20/2 based in my observation, has a single ground connection point on the back right side, with a wire connected (maybe factory done?) from there to the AC motor. In other words: From point A to point B in the same table. That cable does not go outside the 20/2.

2. On top of the ground wire detailed above (point 1), There are two different wires running ground connectors: 

2.a. Tonearm: This is the one which runs from the tonearm, together with the RCAs. All of them should be plugged in straight to the back of the MA12000 MC inputs. That's easy; similarly to the DIN connector into the 20/2 DIN socket. But the ground wire is still disconnected (is a very small satin nickel colored (maybe silver)/ material with a closed rounded shape - wire is very short, maybe extends just 3 inches from the DIN connector). My question still: Where that ground wire should be connected to the 20/2, since the end is connected to the MA12000 inputs.

2.b. There is another ground wire, which is externally attached to the wire which runs from the SME Power Supply/ Speed Control Unit to the table. Its connector is maybe "gold platted" with a closed rounded shape The I don't know either where that ground connector should be attached to the table. 

Anyway, as I said before: I don't have humming of any kind, but I'm not comfortable with ground's wires unconnected, just hanging from behind the table. I took several pictures to better explain this case, but looks like that AG does not allows picture's attachment. 

I’m not sure if they will help you, though. The SME cables that came with my arms have two ground wires. The one that leaves the bundle near the plug that goes into the base of the tonearm is to be connected to a ground on your pre-amp. The other ground wire, that leaves the bundle close to the RCA plugs is connected to a ground on your phono stage. If you don’t have a separate phono stage you have to experiment with connecting one, or the other, or both to the ground on the pre-amp, and go with whichever option doesn’t cause any hum.

If you have both of those ground wires connected you should not connect a ground wire to any ground terminal on the turntable, if present, as this will cause a ground loop and humming.

Here is the 20/2 Manual:

https://sme.co.uk/wp-content/uploads/2016/12/SME-model-20-2-instructions.pdf

and for the Series IV tonearm:

https://sme.co.uk/wp-content/uploads/2016/12/SME-series-iv-instructions.pdf

The ground wire at the RCA end should be connected at the grounding post on your phonostage.

Here ya go!

https://sme.co.uk/wp-content/uploads/2016/12/SME-series-iv-instructions.pdf